Solid-state transistors are used in a wide variety of applications. For example, solid-state power transistors provide large operating voltages (e.g., 50V) for power supplies, electric cars, and solar cells. As shown in FIG. 1, a power transistor 100 includes a semiconductor substrate 102, substrate regions 103 (drawn in broken lines), and interconnects 105 connected to the substrate regions 103. The substrate regions 103 includes a gate region 103a, a source region 103b, and a drain region 103c. The interconnects 105 include a gate interconnect 105a on the gate region 103a, a source interconnect 105b on the source region 105b, and a drain interconnect 105c on the drain region 103c. In operation, a gate signal at the gate interconnect 105a turns the power transistor 100 “on” by opening a conductive channel in the gate region 103a. When the conductive channel is open, a voltage across the source and drain interconnects 105b, 105c draws an electrical current through the conductive channel. When the power transistor 100 is “off,” the gate signal closes the conductive channel so that the electrical current ceases to flow.
In general, a transistor will operate more efficiently per unit area with a small footprint (i.e., when it occupies a small surface area). Certain design constraints, however, make it difficult to reduce the footprint of a transistor. These design constraints particularly impact power transistors. Referring again to the power transistor 100, one design constraint requires the substrate regions 103 and the interconnects 105 to have a serpentine shape. The serpentine shape winds the gate region 103a around the surface of the substrate 102 to maximize the magnitude of the operating current. Another design constraint requires the interconnects 105 to be spaced apart by a minimum spacing distance S0 to prevent electromigration of the interconnect materials. Because the interconnects 105 wind across the surface of the substrate 102, however, the spacing distance S0 has a substantial impact on the footprint.